Casualty reports are still coming in from the six provinces that have reported attacks, but initial indications are that 20 to 35 people have been killed and up to 100 have been injured.
The biggest attack came in the northern city of Kirkuk, where two bombs targeting police killed four people and injured 24.
Interior Ministry sources said 17 people have been killed in five separate bomb blasts in and around Baghdad, including one targeting the convoy of Health Minister Majid Hamed Amin.
Other bombs were reported in Baquba, Samarra, Tarmiyah, Taji, Ramadi, and Malha.
It is the deadliest day in Iraq since 50 people were killed and 255 injured in a nationwide spate of bombings claimed by an Al-Qaeda-connected group, the Islamic State of Iraq.